1. Field of the Invention
The present invention relates to a resist composition, a method of forming a resist pattern using the resist composition, a novel polymeric compound and a compound useful as a monomer for the polymeric compound.
Priority is claimed on Japanese Patent Application No. 2010-267327, filed Nov. 30, 2010, the content of which is incorporated herein by reference.
2. Description of Related Art
In lithography techniques, for example, a resist film composed of a resist material is formed on a substrate, and the resist film is subjected to selective exposure of radial rays such as light or electron beam through a mask having a predetermined pattern, followed by development, thereby forming a resist pattern having a predetermined shape on the resist film.
A resist material in which the exposed portions become soluble in a developing solution is called a positive-type, and a resist material in which the exposed portions become insoluble in a developing solution is called a negative-type.
In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have led to rapid progress in the field of pattern miniaturization.
Typically, these miniaturization techniques involve shortening the wavelength (and increasing the energy) of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays KrF excimer lasers and ArF excimer lasers are now starting to be introduced in mass production. Furthermore, research is also being conducted into lithography techniques that use an exposure light source having a shorter wavelength (and a higher energy level) than these excimer lasers, such as an electron beam, extreme ultraviolet radiation (EUV), and X-ray.
Resist materials for use with these types of exposure light sources require lithography properties such as a high resolution capable of reproducing patterns of minute dimensions, and a high level of sensitivity to these types of exposure light sources.
As a resist material which satisfies these conditions, a chemically amplified resist composition is used, which includes a base component that exhibits a changed solubility in a developing solution under the action of acid and an acid generator component that generates acid upon exposure.
For example, when the above developing solution is an alkali developing solution (when the process is an alkali developing process), a chemically amplified positive resist composition typically contains a resin component (base resin) that exhibits increased solubility in an alkali developing solution under the action of acid, and an acid generator component. If the resist film formed using this resist composition is selectively exposed during formation of a resist pattern, then acid is generated from the acid generator component within the exposed portions, and the action of this acid causes an increase in the solubility of the resin component in an alkali developing solution, making the exposed portions soluble in the alkali developing solution. On the other hand, the unexposed portions remain. As a result, a positive pattern is formed. Here, a resin that exhibits increased polarity by the action of acid has been used as the base resin, and the solubility in an alkali developing solution increases while the solubility in an organic solvent reduces. For this reason, if a process (hereafter, sometimes referred to as a “solvent developing process” or “negative developing process”) using a developing solution containing an organic solvent (organic developing solution) is employed instead of the alkali developing process, the solubility in an organic developing solution is relatively reduced within the exposed portions. As a result, in this solvent developing process, the unexposed portions of the resist film are dissolved and removed by the organic developing solution whereas the exposed portions remain as a pattern, and hence, a negative resist pattern can be formed. For example, a negative developing process has been proposed in Patent Document 1.
Examples of these acid generators usable in a chemically amplified resist composition are numerous, and include onium salt-based acid generators, oxime sulfonate-based acid generators, diazomethane-based acid generators, nitrobenzylsulfonate-based acid generators, iminosulfonate-based acid generators, and disulfone-based acid generators. Of these, as an onium salt-based acid generator, iodonium salts containing iodonium ions as cations and sulfonium salts containing sulfonium ions as cations have conventionally been used.
Currently, resins that contain structural units derived from (meth)acrylate esters within the main chain (acrylic resins) are now widely used as base resins for resist compositions that use ArF excimer laser lithography, as they exhibit excellent transparency in the vicinity of 193 nm. Examples of such resins include a resin containing a structural unit having an acid dissociable, dissolution inhibiting group that is dissociated by the action of acid generated from the acid generator, as well as a structural unit having a lactone structure (for example, refer to Patent Document 2). Structural units having a lactone structure are generally considered as being effective in improving the adhesion between the resist film and the substrate, and increasing the compatibility with an alkali developing solution, thereby contributing to improvement in various lithography properties.
Further, in recent years, resins containing, instead of or in addition to a structural unit having a lactone structure, a structural unit having a cyclic group that includes a —SO2— moiety within the ring skeleton have also been used (for example, refer to Patent Document 3). Further, structural units having a cyclic group that includes a —SO2— moiety within the ring skeleton are generally considered as being effective in improving the adhesion between the resist film and the substrate, and increasing the distribution homogeneity of acid generator within the resist film, thereby contributing to improvement in various lithography properties.